The present invention relates to magnetic printing and more particularly to an improved printing head and magnetic brush configuration for use therein.
Magnetic printing systems are known which utilize a recording head for selectively magnetizing each of a plurality of regions of a magnetizable recording medium for subsequent formation of similar patterns of toner material applied to the medium by a magnetic brush and thence transferred to a hard copy medium, such as paper, to produce printed hard copy in response to electronic signal patterns. As an example, the printing system illustrated in U.S. Pat. No. 3,945,343, entitled "Magnetic Brush for Use in Magnetic Printing", issued Mar. 23, 1976 and assigned to the assignee of the present invention and incorporated herein in its entirety by reference, has a magnetic media drum 14 upon which an image pattern 16 is formed by selective magnetization by a recording head 12; as the drum turns, the selectively magnetized image has dry particulate toner applied to the latent image on the magnetic recording media by a magnetic brush 18 using the exterior surface of the media drum as a bearing surface. The toner image is subsequently transferred to a sheet of paper 26, prior to the drum being cleaned and readied for selective magnetization of a subsequent image thereon. This configuration is undesirable in that both recording head and magnetic brush work upon the same surface of the media and may allow an amount of the toner, not cleaned from the drum, to reach the recording head and reduce the printing field produced thereby and/or to cause background stipling of the recorded image. Further, as both recording head magnetic brush operate upon the same surface of the recording media, the two elements must be positioned in spaced apart relationship, whereby extraneous particles of toner and other materials may be deposited upon the latent image between the time of recording the latent image and applying a toner thereto. This arrangement is further undesirable in that high speed image printing desirably replaces the drum with a driven belt of magnetic recording media (to achieve reproducible recording-head-to-media spacing) and must then require a support member on the opposite side of the belt from the magnetic brush to maintain proper gap relationships and to support the media against the working surface of the magnetic brush. A magnetic printer reducing the number of elements required for facilitating the recording and toner-application functions, to reduce cost and facilitate manufacture, is highly desirable.